Written by John Carroll

Prothena Corp. (Nasdaq: PRTA) turned up at the big Alzheimer’s/Parkinson’s conference in Vienna over the weekend to detail early-stage data showing how its Roche-partnered drug PRX002/RG7935 (Roche inked a $600 million deal on this drug with Prothena in 2013) can flush out toxic clusters of alpha-synuclein in Parkinson’s patients - and they used the occasion to note the launch of their Phase II study.

Investigators in the Phase Ib trial (primarily Baylor’s Joseph Jankovic) used multiple ascending doses of PRX002/RG7935 in Parkinson’s patients and found that a single dose could slash free serum alpha-synuclein levels by up to 97%, with the response maintained after two monthly doses...[Such] a snapshot of biomarker activity [though]...is certainly no guarantee of success in mid-stage trials...[as] companies like Roche have been trying, without success over the last 14 years, to modify Alzheimer’s by removing amyloid beta in the brain — which is a related strategy...[these results were] what these two partners were looking for before moving into Phase II

The drug is a standout in the field, which has been centered heavily on add-on drugs to the symptomatic therapy levodopa in reducing “OFF” times. Newron just obtained an approval for Xadago, which fits into the new class of symptomatic add-ons.

Roche and Prothena will now launch the Phase II in the second quarter, looking for efficacy data for an antibody that targets alpha-synuclein, which some believe triggers Parkinson’s after it aggregates in the brain, causing pathological changes in healthy neurons.

Prothena certainly isn’t alone in focusing on alpha-synuclein, however, as several of its rivals are also targeting Alzheimer’s. Switzerland’s AC Immune SA (Nasdaq: ACIU), partnered with Roche on AD, and Sweden’s BioArctic are focused on the same target, along with Prana Biotechnology Ltd. (Nasdaq: PRAN) and Proclara.